Gas turbine, combined cycle plant and compressor

ABSTRACT

A gas turbine, a combined cycle plant and compressor by which both augmentation of the power output and augmentation of the thermal efficiency can be realized by injecting liquid droplets into inlet air introduced into an entrance of a compressor with simple equipment which is suitable for practical use. The gas turbine includes a compressor for taking in and compressing gas, a combustor in which fuel is combusted with the gas discharged from the compressor, and a turbine driven by the combusted gas of the combustor. The gas turbine further includes a liquid droplet injection device provided on the upstream side of the compressor for injecting liquid droplets into inlet air to be supplied into the entrance of the compressor to lower the temperature of the inlet air to be introduced into the compressor so that the injected liquid droplets may be evaporated while flowing through the compressor.

This is a continuation application of U.S. Ser. No. 08/767,813, filedDec. 17, 1996, now U.S. Pat. No. 6,378,284.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gas turbine, and more particularly to a gasturbine wherein liquid droplets are injected into compressor inlet airof the gas turbine. The present invention further relates to a combinedcycle plant, and more particularly to a combined cycle plant whereinliquid droplets are injected into inlet air of a compressor of thecombined cycle plant. The present invention relates also to acompressor, and more particularly to a compressor wherein liquiddroplets are injected into compressor inlet air.

2. Description of the Related Art

When the air temperature rises in summer or the like, the power outputof a gas turbine drops, and various constructions are disclosed for amethod of power recuperation.

In Japanese Patent Laid-Open Application No. Hei 7-97933, JapaneseUtility Model Laid-Open Application No. Sho 61-37794 or Japanese PatentLaid-Open Application No. Hei 5-195809, it is disclosed to coolcompressor inlet air.

Meanwhile, in Japanese Patent Laid-Open Application No. Sho 61-283723,it is disclosed to supply water from an entrance of a compressor and amid stage of the compressor in a combined system of a gasificationfurnace and a gas turbine.

Further, in Japanese Utility Model Laid-Open Application No. Sho56-43433, it is disclosed to provide a supply hole for water droplets ina compressor, and in Japanese Patent Laid-Open Application No. Hei2-211331, a gas turbine which includes two high pressure and lowpressure compressors and an intercooler provided between the compressorsis disclosed. Meanwhile, in Japanese Patent Laid-Open Application No.Hei 6-10702, an apparatus is disclosed wherein, in a compressor groupwhich includes a plurality of compressor stages, water is injected intoan intermediate location between the compressor stage on the upstreamand the compressor stage on the downstream in order to reduce powerconsumption.

However, Japanese Patent Laid-Open Application No. Hei 7-97933, JapaneseUtility Model Publication Application No. Sho 61-37794 or JapanesePatent Laid-Open Application No. Hei 5-195809 merely discloses to dropthe temperature of inlet air to be introduced into a compressor in orderto augment the power output. Although it is disclosed in Japanese PatentLaid-Open Application No. Sho 61-283723 to evaporate liquid dropletsduring compression to utilize them as a medium for cooling the blades ofa turbine and to augment the turbine cycle characteristic, it does notachieve both of power augmentation and thermal efficiency augmentation.

For a gas turbine, a combined cycle plant or a compressor, it isdemanded to achieve both of power augmentation and thermal efficiencyaugmentation.

Meanwhile, in order to achieve both effects of augmentation of the poweroutput and thermal efficiency augmentation as in Japanese PatentLaid-Open Application No. Hei 6-10702 or-Japanese Patent Laid-OpenApplication No. Hei 2-21133, a specific equipment is required for a flowpath of high pressure gas at an intermediate portion of a compressor,and there is a problem in that the compressor configuration iscomplicated and increased in scale as a whole. Further, in JapaneseUtility Model Laid-Open Application No. Sho 56-43433, a casing andnozzles in a compressor are required to have a special construction.

Where an actual gas turbine, combined plant and compressor are takeninto consideration, it is demanded that power augmentation and thermalefficiency augmentation can be achieved with simple equipment.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a gas turbine, acombined plant and a compressor by which both of augmentation of thepower output and augmentation of the thermal efficiency can be achievedby injecting liquid droplets into inlet air introduced into an entranceof a compressor.

In order to attain the object described above, according to an aspect ofthe present invention, there is provided a gas turbine, comprising acompressor for compressing and discharging gas supplied thereto, acombustor in which fuel is combusted with the gas discharged from thecompressor, a turbine driven by the combusted gas of the combustor, anda liquid droplet injection device for injecting liquid droplets into gasto be supplied into the compressor to make the temperature of the gas tobe introduced into the compressor lower than the temperature of externalor ambient air so that the injected liquid droplets introduced into thecompressor together with the gas may be evaporated while flowing throughthe compressor.

With the gas turbine, liquid droplets can be injected into inlet air tobe introduced into the entrance of the compressor on power demand toachieve both of augmentation of the power output and augmentation of thethermal efficiency with simple equipment which is suitable for practicaluse.

According to another aspect of the present invention, there is provideda gas turbine, comprising a compressor for compressing and discharginggas supplied thereto, a combustor in which fuel is combusted with thegas discharged from the compressor, a turbine driven by the combustedgas of the combustor, and a liquid droplet injection device provided onthe upstream side of the compressor for injecting liquid dropletsprimarily having droplet diameters of 50 μm or less into gas to besupplied to the compressor.

With the gas turbine, fine liquid droplets can be supplied into inletair to the compressor by simple equipment which is suitable forpractical use, and water droplets can be conveyed well by an inlet airflow to be supplied to the compressor. Accordingly, gas which containsliquid droplets can be transported efficiently from the entrance of thecompressor into the compressor. Further, the liquid droplets introducedinto the compressor can be evaporated in a good state. Consequently,augmentation of the power output and augmentation of the thermalefficiency can be achieved.

According to a further aspect of the present invention, there isprovided a combined cycle plant, comprising a gas turbine including acompressor for compressing and discharging gas supplied thereto, acombustor in which fuel is combusted with the gas discharged from thecompressor, a turbine driven by the combusted gas of the combustor, aheat recovery boiler for generating steam using exhaust gas from theturbine as a heat source, a steam turbine driven by the steam generatedby the heat recovery boiler, and a liquid droplet injection device forinjecting liquid droplets into gas to be supplied to the compressor ofthe gas turbine to make the temperature of the gas entering thecompressor lower than the temperature of external or ambient air so thatthe injected liquid droplets introduced into the compressor togetherwith the gas may be evaporated while flowing through the compressor.

With the combined cycle plant, the thermal efficiency can be augmentedwhile also the power output can be augmented on power demand.

According to a still further aspect of the present invention, there isprovided a compressor to which gas is supplied and which compresses anddischarges the supplied gas, comprising a liquid droplet injectiondevice for injecting liquid droplets into gas to be supplied to anentrance of the compressor to make the temperature of the gas enteringthe compressor lower than the temperature of external air so that theinjected liquid droplets introduced into the compressor together withthe gas may be evaporated while flowing down in the compressor.

With the compressor, driving power for the compressor can be reduced bysimple equipment which is suitable for practical use.

According to a yet further aspect of the present invention, there isprovided a liquid droplet injection device for injecting liquid dropletsinto gas to be supplied to a compressor of a gas turbine which includesthe compressor for compressing and discharging gas supplied thereto, acombustor in which fuel is combusted with the gas discharged from thecompressor, and a turbine driven by the combusted gas of the combustor,wherein the liquid droplet injection device injects liquid droplets tomake the temperature of the gas entering the compressor lower than thetemperature of external air so that the injected liquid dropletsintroduced into the compressor together with the gas may be evaporatedwhile flowing through the compressor.

With the liquid droplet injection device, both of augmentation of thepower output and augmentation of the thermal efficiency of a gas turbineor the like in which the present apparatus is disposed can be achieved.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings inwhich like parts or elements are denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of the present invention;

FIG. 2 is a similar view showing another embodiment of the presentinvention;

FIG. 3 is a similar view showing a further embodiment of the presentinvention;

FIG. 4 is a diagram illustrating a temperature distribution ofcompressed air in a compressor;

FIG. 5 is a diagram illustrating a relationship between the airtemperature and the absolute humidity on a psychrometric chart in acompressor process;

FIG. 6 is a diagram illustrating a relationship between the inlet airtemperature and the inlet air mass flow rate;

FIG. 7 is a diagrammatic view illustrating thermal cycle diagrams of thepresent invention and other methods for comparison;

FIG. 8 is a schematic view showing a detailed structure of a gasturbine;

FIGS. 9(a) and 9(b) are diagrams illustrating a relationship between thewater drop injection amount and the increasing ratio of the power outputof the gas turbine;

FIG. 10 is a diagrammatic view illustrating a relationship between theaxial velocity and the velocity triangle;

FIG. 11 is a schematic view showing an arrangement of atomizing nozzlesin an inlet air compartment; and

FIG. 12 is a diagram illustrating a difference between compressordischarge temperatures before and after injection.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

A first embodiment of the present invention will be described withreference to FIG. 1.

A gas turbine of the embodiment of the present invention includes, asshown in FIG. 1, a compressor 1 for compressing and discharging gas, acombustor 5 to which the gas compressed by the compressor 1 is supplied,a turbine 2 driven by the combustion gas from the combustor 5, agenerator 3 connected to a shaft of the turbine 2, and a electric powergrid 4 for transmitting power generated by the generator 3. Exhaust gas7 from the gas turbine is discharged into the atmospheric air through astack 8.

In the following embodiment, it is assumed that the gas supplied to thecompressor 1 is air.

An inlet air compartment 10 for taking in inlet air 6 to be supplied tothe compressor 1 is connected to the compressor 1. Usually, a louver 9disposed on the upstream side of the inlet air compartment 10. An airfilter 9A is disposed adjacent the louver 9 on the compressor side (rearflow side). The air filter is provided immediately rearwardly of theposition of the louver 9.

While the form wherein the louver 9 is disposed on the upstream side ofthe inlet air compartment is shown in FIG. 1, where the air filter islocated intermediately of the intake air compartment, the inlet aircompartment 10 in the present embodiment presents an inlet air path tothe entrance of the compressor on the downstream side of the air filter.

While the compressor 1, the turbine 2 and the generator 3 are connectedto a common shaft in FIG. 1, the compressor 1 and the turbine 2 mayotherwise have different shafts.

It is to be noted that, in FIG. 1, reference character T1 denotes aninlet air temperature 20 before the inlet air enters the compressor 1,T2 a compressor discharge air temperature 21, T3 a combustiontemperature 22, and T4 an exhaust gas temperature 23 exhausted from theturbine 2.

Unless otherwise specified, those of numerals mentioned herein belowwhich are same as those mentioned above denote the same objects.

The first embodiment further includes a liquid droplet injection devicewhich discharges fine droplets into the inlet air compartment 10. Forexample, an atomizing nozzle 11 is disposed in the inlet aircompartment. The Sauter mean particle diameter (S.M.D.) of liquiddroplets discharged is, for example, approximately 10 μm. Feed watermeans 13 is connected to the atomizing nozzle 11. Where the atomizingnozzle 11 includes atomization means for producing such fine droplets,only the feed water means 13 may be connected, but atomization means mayotherwise be provided in addition to the atomizing nozzle 11. Aconstruction which includes separate atomization means will behereinafter described in greater detail.

The feed water means 13 has a control valve 15 for controlling the flowrate, a feed water pump 16, a feed water tank 17, and a feed waterequipment 18 for supplying water to the feed water tank 17.

The control valve 15 is electrically connected to a function generator24 to which a signal based on the power output of the generator 3 and aload instruction signal Pd 25 are inputted via an addition section andwhich outputs an opening signal for the control valve 15 or the like andother instructions. The control valve 15 is communicated with thefunction generator 24 by a signal cable 26 or the like. In some cases,the load instruction signal Pd 25 may be introduced into the functiongenerator 24.

The inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, and water of the feed water tank 17 passes through thecontrol valve 15 of a predetermined opening and passes the feed watermeans 13 so that fine droplets are discharged from the atomizing nozzle11. Where air supply from air supply means 12 is required in order todischarge fine droplets, a control valve 14 is additionally controlledto a predetermined opening to control the particle diameter ofdischarged liquid droplets. The inlet air 6 contains the liquid dropletsto form a mist flow and enters the compressor 1 after the mist flow ispartially evaporated to cool the inlet air. The liquid dropletscontained in the inlet air are evaporated in the inside of thecompressor 1 and cool the compressed air.

FIG. 4 shows a temperature distribution of compressed air in thecompressor. The air temperature T21 at the exit of the compressor 1exhibits a larger amount of drop in a case 28 wherein water is injectedand water droplets are evaporated in the compressor 1 than another case27 wherein no water droplets are injected. Also in the compressor, theair temperature T21 exhibits a continuous drop.

After the liquid droplets are substantially evaporated in the compressor1, the compressed air is mixed with fuel and the fuel is combusted inthe combustor 5 to form gas of a high temperature and a high pressure,which flows into and works in the turbine 2. The mechanical energy ofthe turbine 2 is converted into electric energy by the generator 3, andthe electric energy is fed to the electric power grid 4. The exhaust gas7 after the work is completed is discharged into the atmospheric airthrough the stack 8.

By the present embodiment, power output augmentation can be achieved andthermal efficiency can be augmented.

The power output increasing mechanism according to the presentembodiment can be summarized qualitatively in the following manner.

1) Cooling of inlet air, which is to be introduced into the compressor1, along a constant wet bulb temperature line on a psychrometric chartin the inlet air compartment 10, 2) cooling of internal gas byevaporation of liquid droplets introduced into the compressor 1, 3) adifference between amounts of working fluid passing through the turbine2 and the compressor 1 which corresponds to an evaporation amount in thecompressor 1, 4) an increase in isobaric specific heat of mixture causedby mixture of air and steam which has a higher isobaric specific heatthan that of pure air, and so forth.

FIG. 11 shows an outline of arrangement of the atomizing nozzle 11 inthe inlet air compartment 10.

A large number of atomizing nozzles 11 are arranged in a predeterminedimaginary section of the inlet air flow path. For example, they arearranged in a plane substantially perpendicular to a flowing directionof inlet air. The atomizing nozzles 11 are arranged such that thedistances between adjacent ones of them may be equal to each other inthe longitudinal direction of the cross section of the inlet air path.Meanwhile, the atomizing nozzles 11 are arranged such that the distancesbetween adjacent ones of them may be equal to each other in the lateraldirection of the cross section of the inlet air flow path. As a whole, alarge number of atomizing nozzles 11 can be arranged in a region of theinlet air compartment 10 forming the inlet air flow path except portionsin the proximity of wall faces as seen in FIG.

The distances between the adjacent ones of the injection nozzles can beset in a similar manner also in the other embodiments.

By the arrangement, water droplets can be distributed homogeneously intoinlet air to be conveyed to the entrance of the compressor.

Meanwhile, in a conventional inlet air cooling apparatus which includesatomizing nozzles outside an inlet air compartment or on the upstreamside of an air filter, since the evaporation efficiency is low,injection of a large amount of water is required, and therefore, arecovery apparatus which recovers almost all of injected liquid and alarge scale circulation system which supplies the recovered liquid tothe atomizing nozzles 11 again are provided usually. However, in thepresent embodiment, there is an advantage also in that, since theevaporation efficiency can be augmented to a value close to 1, no suchlarge scale equipment need be provided.

The atomizing nozzles 11 are positioned on the downstream side withrespect to the air filter of the louver 9. Consequently, the liquiddroplets can be supplied on a flow of inlet air stably to the compressor1. This is because the possibility that, where liquid droplets aresupplied to the upstream side, water droplets may adhere to the airfilter of the louver 9 or the air filter may suffer from choking can besuppressed.

Further, the atomizing nozzles 11 are preferably disposed at a distancefrom the entrance of the compressor 1 taking an evaporation amount whenliquid droplets flow in the inlet air compartment 10 and so forth intoconsideration. Where a so-called IGV (inlet guide vane) is disposed atthe entrance of the compressor 1, the atomizing nozzles 11 are disposedon the upstream side of the IGV. It is to be noted that, where asilencer or the like is provided, the atomizing nozzles 11 arepositioned on the downstream side of the silencer or the like.

On the other hand, where the atomizing nozzles 11 are disposed in theproximity of the boundary between the compressor 1 and the inlet aircompartment 10, if fine droplets are to be injected into the inlet air,it is easy to produce liquid droplets of small particle diameters toenter the compressor.

For example, evaporation of liquid droplets can begin with a stagenearer to the first stage side to effectively perform reduction of thedriving power of the compressor.

FIG. 8 is a schematic view showing a detailed structure of a gas turbineto which the present invention is applied. Liquid droplets injected intoinlet air from the atomizing nozzles 11 flow on an air flow into thecompressor through the entrance. The average air flow speed of inlet airflowing in the inlet air compartment is, for example, 20 m/s. Liquiddroplets 37 move on gas paths of the compressor 1 along stream lines. Inthe compressor, the inlet air is heated by adiabatic compression, andwhile the liquid droplets are evaporated from the surfaces thereof bythe heat, they are transported to the rear stage blade side whiledecreasing the particle diameters thereof. In this process, since thelatent heat of evaporation necessary for evaporation is supplied fromthe air (sensible heat) in the compressor, the temperature of the air inthe compressor drops by a larger amount than where the present inventionis not applied (refer to FIG. 4). If the particle diameters of theliquid droplets are large, the liquid droplets will collide with theblades or the casing of the compressor 1 and acquire heat from the metalso that they are evaporated, and consequently, the temperaturedecreasing effect of the working fluid may possibly be hindered.Therefore, from such a point of view, preferably the particle diametersof liquid droplets are small.

A distribution in particle diameter is present with injected liquiddroplets. From the point of view of suppression of collision with theblades or the casing of the compressor 1 or prevention of erosion of theblades, liquid droplets to be injected are controlled so that they mayhave particle diameters principally of 50 μm or less. From the point ofview of reduction of an influence acting upon the blades, preferably theliquid droplets are controlled so that the largest particle diameter maybe equal to or smaller than 50 μm.

Furthermore, since liquid droplets having smaller particle diameters canbe distributed more homogeneously into flowing-in air, and from thepoint of view of suppression of production of a temperature distributionin the compressor, the particle diameters are preferably set to 30 μm orless in Sauter mean particle diameter (S.M.D.). Since liquid dropletsinjected from the injection nozzles have a distribution in grain size,measurement is not easy with the largest particle diameter mentionedabove, and therefore, for practical use, a result of measurement withthe Sauter mean particle diameter (S.M.D.) as described above can beused. It is to be noted that, although preferably the particle diametersare small, since the injection nozzles which produce liquid droplets ofsmall particle diameters require a high precision production technique,the range of the particle diameter for practical use is defined by atechnically available lower limit therefore, from such a point of viewas just described, the lower limit to, for example, the principalparticle diameter, the largest particle diameter or the average particlediameter is 1 μm. Further, since the energy for production of liquiddroplets in most cases increases as the particle diameter thereofdecreases, the lower limit may be determined by taking the energy usedfor production of liquid droplets into consideration. Where the particlediameter of liquid droplets is set to a value around which the liquiddroplets float in the atmospheric air and do not drop readily, theliquid droplets usually exhibit good heat transfer characteristics.

As liquid droplets are evaporated, the mass flow rate of the workingliquid increases. If the evaporation in the compressor is completed,then the gas in the compressor 1 is further subject to adiabaticcompression. In this instance, since the isobaric specific heat of thewater steam has a value substantially equal to twice that of the airaround a representative temperature (300° C.) in the compressor, thewater steam has an effect in heat capacity equivalent to that obtainedwhere, in conversion into air, an amount of air having a weightapproximately twice that of water droplets to be evaporated is increasedas the working fluid. In particular, there is an effect (heat risesuppression effect) in drop of the discharge air temperature T2 of thecompressor. An action that the discharge air temperature of thecompressor is dropped by evaporation of water droplets in the compressoroccurs in this manner. Since the power of the compressor is equal to adifference between enthalpies of air at the entrance and the exit of thecompressor and the enthalpy of air increases in proportion to thetemperature, as the air temperature at the exit of the compressor drops,the required work for the compressor can be reduced.

The working fluid (air) pressurized by the compressor is raised intemperature by combustion of fuel in the combustor and then flows intothe turbine, in which it performs an expanding work. This work is calledshaft power of the turbine and is equal to a difference betweenenthalpies of air at the entrance and the exit of the turbine. Thesupply amount of the fuel is controlled so that the gas temperature atthe entrance of the turbine may not exceed a predetermined temperature.For example, a turbine entrance temperature is calculated from anexhaust gas temperature at the exit of the turbine and a measured valueof the pressure Pcd at the exit of the compressor, and the fuel flowrate to the combustor 5 is controlled so that the calculated value maybe equal to a value obtained before the present invention is applied. Ifsuch constant combustion temperature control is effected, then the fuelsupply amount is increased by an amount corresponding to a drop of thegas temperature T2 at the exit of the compressor as described above.Further, if the combustion temperature is invariable and the weightratio of injected water is approximately several percent with respect tothe inlet air, since the pressure at the entrance of the turbine and thepressure at the exit of the compressor are approximately equal beforeand after injection is performed, also the gas temperature T4 at theexit of the turbine does not exhibit a variation. Consequently, theshaft power of the turbine does not exhibit a variation before and afterinjection. On the other hand, since the net power output of the gasturbine is a difference of the power of the compressor from the shaftpower of the turbine, after all, by applying the present invention, thenet power output of the gas turbine can be increased by an amountcorresponding to a reduced amount of the power of the compressor.

The electric output QE of the turbine 2 is obtained by subtracting thework Cp (T2−T1) of the compressor 1 from the shaft power Cp (T3−T5) ofthe turbine 2 and can be represented approximately by the followingexpression (1):

Q _(E) /Cp=T 3−T 4−(T 2−T 1)  (1)

Normally, since operation is performed so that the combustiontemperature T3 may be constant the gas turbine output temperature T4does not exhibit a variation, and also the shaft power Cp (T3−T4) of theturbine is constant. In this instance, if the compressor exittemperature T2 drops to T2′ (<T2) as a result of mixture of water mist,a power increase T2−T2′ equivalent to a drop of the work of thecompressor is obtained. Meanwhile, the thermal efficiency η of the gasturbine is given approximately by the following expression (2):$\begin{matrix}{\eta = {1 - \frac{{T4} - {T1}}{{T3} - {T2}}}} & (2)\end{matrix}$

In this instance, since T2′<T2, the second term on the right side issmall, and it can be seen that also the thermal efficiency is augmentedby injection of water. In other words, while the heat energy Cp (T4−T1)(the numerator of the second term of the expression 2) exhausted from aheat engine, that is, the gas turbine, to the outside of the system doesnot exhibit a great difference before and after application of thepresent invention, where the present invention is applied, the fuelenergy Cp (T3−T2′) supplied increases by an amount equal to Cp (T2−T2′),that is, a drop of the work of the compressor. Meanwhile, since theamount of the drop of the work of the compressor is equal to the poweroutput increase as described above, it is considered that the increasedamount of the fuel substantially entirely contributes to an increase ofthe power output of the gas turbine. In this manner, the increasedamount of the power output provides a thermal efficiency of 100%.Consequently, the thermal efficiency of the gas turbine can beaugmented. In this manner, in the present embodiment, in order to reducethe work of the compressor which is not disclosed explicitly in theprior art wherein inlet air is cooled, an increase of the total poweroutput of the gas turbine can be anticipated by mixing water mist intoinlet air of the compressor 1. On the other hand, while the prior artwherein water is injected into the entrance of a combustor contemplatesincrease of the power output by increasing the working fluid, since thework of the compressor 1 is not decreased, the thermal efficiency isdropped conversely.

FIG. 7 illustrates a heat cycle of the present invention and anotherheat cycle for comparison. The area of a closed region of a cycle chartindicates a gas turbine power output per unit inlet air flow rate, thatis, a specific power output. Reference numerals in FIG. 7 denote theworking fluid at the corresponding locations of the cycle charts. InFIG. 7, reference numeral 1 denotes the entrance of the compressor, 1′the entrance to an intercooler from the first stage compressor, 1″ theentrance of the second stage compressor after working fluid goes outfrom the intercooler, 2 the entrance of the combustor in a Braytoncycle, 2′ the entrance of the combustor after the working fluid goes outfrom the second stage compressor, 3 the entrance of the turbine afterthe working fluid goes out from the combustor, and 4 the exit of theturbine.

The temperature T-entropy S charts in the lower stage of FIG. 7illustrate comparison in characteristic where the values of thetemperature T-entropy S at the positions 1, 3 and 4 of the cyclesdescribed above are fixed.

As seen from FIG. 7, the magnitude of the specific power outputdecreases in order of that obtained by injecting fine water dropletsmentioned hereinabove in an inlet air compartment of a compressor tointroduce water droplets through the entrance of the compressor as inthe present embodiment, that obtained by such an intercooling cycle asdisclosed in Japanese Patent Laid-Open Application No. Hei 6-10702, andthat obtained by an ordinary Brayton cycle. Particularly, the differencebetween the specific power outputs by the intercooling cycle and thepresent invention originates from the fact that, according to thepresent invention, water droplets introduced into the compressor arecontinuously evaporated from the entrance portion of the compressor, andthis appears in the shapes of the cycles.

While the thermal efficiency of the intercooling cycle is inferior tothat of the Brayton cycle, the present embodiment is superior to theBrayton cycle as described hereinabove, and consequently, the presentinvention achieves a higher thermal efficiency than the intercoolingcycle.

Generally, as the position at which injected liquid droplets areevaporated in the compressor 1 approaches the entrance of the compressor1, the air temperature at the exit of the compressor 1 drops, which issuperior in terms of increase in power output and thermal efficiencyaugmentation. Accordingly, where the method wherein injected liquiddroplets are mixed into the inlet air 6 is employed, the effectincreases as the particle diameters of the injected liquid dropletsdecrease. This is because mist is evaporated quickly after it flows intothe compressor 1. Further, the injected liquid droplets float in the airand are introduced smoothly into the compressor together with the inletair.

Consequently, liquid droplets injected from the atomizing nozzles 11preferably have such a size that substantially all of them areevaporated before they come to the exit of the compressor 1.Practically, the size of liquid droplets may be such that they areevaporated by less than 100% but by an upper limit which can be achievedby the construction described above. In practical use, liquid dropletsshould be evaporated by 90% or more at the exit of the compressor.

For example, when the discharge pressure P_(cd) of the compressor 1 is0.84 MPa, if the evaporation ratio is calculated taking a correlationbetween measurement values of an absolute humidity at the exit of thecompressor 1 and another absolute humidity at the position of IGVestimated from the ambient conditions into consideration, then theliquid droplets are evaporated by 95% or more before they come to theexit of the compressor.

The time within which air passes through the compressor is short, and inorder to allow liquid droplets to be evaporated well within the time toraise the evaporation efficiency, preferably the particle diameter ofthe liquid droplets should be 30 μm or less in Sauter mean particlediameter (S.M.D.).

It is to be noted that, since atomizing nozzles which make liquiddroplets of small particle diameters require a manufacturing techniqueof a high degree of accuracy, the lower limit to the particle diameteris given by a lower limit which can be achieved technically.Accordingly, the lower limit to the particle diameter is, for example, 1μm.

This is because, where the liquid droplets are excessively large, it isdifficult to evaporate liquid droplets well by the compressor.

The amount of liquid droplets to be introduced can be adjusted by thetemperature and the humidity or a degree of the increase of the poweroutput. Taking an amount by which injected liquid droplets areevaporated within a range from the injection location to the entrance ofthe compressor into consideration, liquid droplets can be introduced byan amount equal to or more than 0.2 weight % of the mass of the inletair. The upper limit is determined so that the functions of thecompressor can be maintained good. For example, the upper limit may beset to 5 weight %, and the range of introduction can be set lower than 5weight %.

While adjustment is possible taking a summer season or the like or adrying condition or the like into consideration, in order to achieve afurther increase in power output and so forth, liquid droplets may beintroduced by a rate equal to or higher than 0.8 weight % but equal toor lower than 5 weight %.

Comparing with a conventional liquid droplet injection device of thetype wherein liquid droplets (for example, 100 to 150 μm and so forth)are merely injected into introduced air in order to lower thetemperature of air to be introduced into the entrance of a compressorand, after the injection, the water is recovered and utilized forinjection again, it is required to inject only a small amount of liquiddroplets in the present embodiment.

The consumption amount of injection water exhibits a maximum used amountwhere the power output drops when it is high in temperature in summerand is to be recuperated to a rated power output. The consumption amountof pressurized air when air is supplied upon formation of mist cannot beignored and should preferably be smaller than the consumption wateramount as a target. Accordingly, only if the particle diameter conditionis satisfied, is it economical that no air is supplied to form liquiddroplets of the particle diameter mentioned above.

Based on the present embodiment, a generating plant which can suppress avariation of the power output all through a year can be provided bycontrolling the flow rate of mist in response to the ambienttemperature. For example, the opening of the control valve 15 isadjusted so that the flow rate of mist is increased when the temperatureof air to be introduced into the compressor is high compared with thatwhen the air temperature is low.

Further, preferably the system is operated so that the liquid dropletsare supplied upon equal combustion temperature operation. By this, thethermal efficiency can be augmented and the power output can beaugmented.

Further, in a gas turbine which is not used for generation or a gasturbine for obtaining torque when it is driven, the combustiontemperature can be lowered to lower the power output of the shaft of theturbine. Particularly upon part load operation, the present embodimentcan be applied to save the fuel.

In the present embodiment, within a range higher than a level to whichthe power output is restricted from the ambient temperature, the poweroutput can be controlled in response to a requested load.

Further, since the power output can be augmented even if the combustiontemperature is not raised, a gas turbine which has a long life can beprovided.

Further, according to the present embodiment, gas in the compressor canbe cooled. Consequently, where this is utilized to use bleed extractionof the compressor for cooling the blades of the gas turbine, the bleedextraction amount for cooling can be reduced. Further, since the amountof the working fluid in the gas turbine can be increased by this, a highthermal efficiency and increase in power output can be anticipated.

In FIG. 1, the load instruction signal Pd 25 can be set to a rated valueso that the flow rate of injected liquid droplets may be automaticallycontrolled.

Subsequently, an operation method and control of the gas turbine will bedescribed.

When it is intended to increase the power output of the gas turbine, thestep of increasing the amount of liquid to be injected from theatomizing nozzles 11 and the step of increasing the amount of fuel to besupplied to the combustor are used. On the other hand, when it isintended to decrease the power output of the gas turbine, the amount ofliquid to be injected is decreased and the amount of fuel to be suppliedto the combustor is decreased.

When it is intended to increase the power output of the gas turbine, theamount of fuel to be supplied to the combustor is increased after theamount of the liquid to be injected is increased. On the contrary, whenit is intended to decrease the power output of the gas turbine, theamount of fuel to be supplied to the combustor is decreased before theamount of liquid to be injected from the atomizing nozzles 11 isdecreased.

An example of operation when the gas turbine is in a base load operationstate will be described below.

Question control when operation with a fixed combustion temperature isperformed may be such as follows. The function generator 24 calculatesan injection water amount so as to correspond to an aimed power outputbased on a load instruction signal Pd 25 and issues an instruction toincrease the opening to the control valve 15. The function generator 24further calculates a compressed air amount necessary for a predeterminedamount of water to be introduced via the control valve 15 to andinjected by the atomizing nozzles 11 and necessary for predeterminedparticle diameters to be obtained, and issues an instruction to increasethe opening to the control valve 15. Consequently, a predeterminedamount of compressed air is introduced into the atomizing nozzles 11through the control valve 15. Meanwhile, the fuel flow rate ismaintained fixed. Subsequently, exhaust gas temperature control isentered to increase the fuel flow rate so that the combustiontemperature (an estimated value may be used) may become equal to itsaimed value.

An exhaust gas temperature control curve which presents an aimed valuefor the exhaust gas temperature during operation may be represented by afunction of the compressor discharge pressure Pcd and the injectionamount or may be an ordinary control curve applied for a case wherein noinjection is involved. Alternatively, a value obtained by adding asuitable bias to an aimed exhaust gas temperature estimated from anordinary control curve may be used.

When the power output of the gas turbine reached in this manner has adeviation from its aimed value, if the power output is to be increased,the injection amount is increased in accordance with the proceduredescribed above, whereafter exhaust gas temperature control is entered.On the other hand, if the power output is to be decreased, the fuel flowrate is reduced first, and then the injection amount is decreased.

Where the function generator 24 which effects such control as describedabove is provided, the power output can be adjusted while preventing thesituation that the combustion temperature exceeds its allowable value.

It is to be noted that, when the power output is to be decreased, thedecreasing of the injection amount may be performed sufficiently slowlycomparing with the increasing of the injection amount which is performedwhen the power output is to be increased in such a manner that the fuelflow rate is decreased in accordance with exhaust gas temperaturecontrol similar to that for the increasing of the power output.

In order to realize an aimed power output, instead of continuouslyvarying the injection amount as described above, operation may beperformed setting the injection amount to a predetermined value takingan amount of rise of the power output based on measured values ofambient conditions such as an ambient temperature and a humidity intoconsideration. For example, the injection amount or the like iscalculated as a function of the ambient temperature, the humidity and anamount of rise of the power output and is set to a desired value.Consequently, also constant injection amount operation wherein theinjection amount is not varied in response to a small variation of thepower output or a variation of the air temperature becomes possible. Thepresent system has an effect in that operation control is facilitated.Further preferably, after a predetermined time elapses after the settingdescribed hereinabove, the ambient conditions are measured again, andre-setting of the injection amount is performed to allow adjustment ofthe amount of rise of the power output comparatively readily inconformity with the ambient conditions.

The operation of the gas turbine described above may be recognized alsoas control of the water droplet injection device for injecting waterdroplets into inlet air to be supplied to the compressor 1 of the gasturbine. Where the water droplet injection device is operated in such amanner as described above, the effect described above can be provided toa gas turbine in which the water droplet injection device is disposed.

The embodiment of FIG. 1 further may include an atomization means forobtaining liquid droplets of the fine particle diameters described abovetogether with the atomizing nozzles 11. The atomization means includesmeans for supplying pressurized air to the atomizing nozzles 11.

More particularly, in addition to the atomizing nozzles 11 provided withfeed water means 13, air supply means 12 are provided for supplyingpressurized air to the atomizing nozzles 11. The air supply means 12includes an accumulator 29 provided separately from the compressor 1 forsupplying pressurized air, and includes a path which introducespressurized air from the accumulator 29 to the atomizing nozzles 11 viaa control valve generally indicated by the numeral 14. The control valve14 controls the flow rate of gas to the atomizing nozzles 11.Specifically, a control valve 14 a for controlling the amount ofpressurized air to be supplied to the injection nozzles is provided.

The control valve 14 and the control valve 15 are electrically connectedto a function generator 24 which receives a signal based on the poweroutput of the generator 3 and a power demand signal Pd 25 via anaddition section and outputs opening signals for the control valve 14,the control valve 15 and so forth and other instructions. The controlvalve 14 and the control valve 15 are connected to the functiongenerator 24, for example, by a signal cable 26 or the like. Dependingupon the case, the power demand signal 25 may be introduced directly tothe function generator 24.

Inlet air 6 comes to the inlet air compartment 10 through the louver 9,and water of the feed water tank 17 passes through the control valve 15of a predetermined opening and is supplied to the atomizing nozzles 11through the feed water means 13. Further, pressurized air produced bythe accumulator 29 is supplied to the atomizing nozzles 11 through thecontrol valve 14 of a predetermined opening. Then, fine liquid dropletsare injected from the atomizing nozzles 11. The nozzles may be of thetype wherein the amounts of air and liquid to be supplied can beadjusted to adjust the particle diameters in a desired range within therange described hereinabove. The inlet air 6 contains the liquiddroplets to form a mist flow and flows into the compressor 1 after partof the mist flow is evaporated to cool the inlet air. The liquiddroplets contained in the inlet air are evaporated in the inside of thecompressor 1 and cool the compressed air.

After the liquid droplets are substantially evaporated in the compressor1, the fuel is mixed and combusted with the compressed air in thecombustor 5 to produce gas of a high temperature and a high pressure,which then flows into and works in the turbine 2. The mechanical energyis converted into electric energy by the generator 3, and the electricenergy is fed to the electric power grid 4. The exhaust gas 7 aftercompleting the work is discharged to the atmospheric air through thestack 8.

Since the separate accumulator 29 is provided, the power of thecompressor is not decreased, and in addition to the effects ofaugmentation of the power output of the gas turbine and augmentation ofthe thermal efficiency of the gas turbine, a further effect is sometimesprovided from the point of view of an arrangement or from the point ofview of power saving.

Further, though not shown in the drawings, the accumulator 29 may supplygas from an atomization compressor for supplying compressed air.

For the nozzles described above, air mist nozzles of the internal mixingtype with which liquid droplets of a desired particle diameter can beobtained, may be used.

Upon operation and control of the gas turbine, when it is intended toincrease the power output of the gas turbine, in addition to theincrease of the amount of water to be injected as described above, theamount of air to be supplied to the atomizing nozzles 11 may beincreased so that the particle diameter of liquid droplets injected fromthe injection nozzles may be of a desired size.

When decreasing the power output, the amount of liquid to be supplied tothe atomizing nozzles 11 is decreased and the amount of air to besupplied to the atomizing nozzles 11 is decreased to adjust the particlediameter of liquid droplets.

Further, in order to facilitate operation, the amount of air and theamount of liquid to be supplied to the atomizing nozzles 11 are notadjusted, but,only the amount of liquid to be supplied may be adjustedwhile the air amount is fixed.

In this instance, the amount of air to be supplied is adjusted so that adesired particle diameter of liquid droplets may be obtained when anallowable maximum amount of liquid is supplied. Consequently, when theamount of liquid to be injected is lower than the maximum injectionliquid amount therefore, the diameter of the liquid droplets is reducedfrom that obtained when the amount of water is the maximum injectionwater amount, and a good condition can be obtained.

Further, in addition to the accumulator 29 described above or withoutthe separate provision of the accumulator 29, the following constructionmay be employed.

The air supply means 12 includes a path which communicates bleedextraction from a mid stage of the compressor 1 with the atomizingnozzles 11 or another path which is branched from a path along whichcompressed air discharged from the compressor 1 flows and iscommunicated with the atomizing nozzles 11. The path includes a controlvalve 14 b for controlling the amount of pressurized air to be supplied.In conformity with a demand to make injection effective or a likedemand, the path may have a cooler 19 for adjusting the temperature ofcompressed air to a desired temperature.

Consequently, where the arrangement described above is provided togetherwith the accumulator 29, the power of the accumulator 29 installedseparately can be reduced by first using bleed extraction from the midstage or discharged air and then using compressed air from theaccumulator 29 for a short amount. Further, where the constructionpreviously described is employed in place of the accumulator 29,simplification of the equipment can be anticipated.

Further, in the construction wherein compressed air from the mid stageof the compressor 1 or compressed air discharged from the compressor 1is supplied in order to atomize liquid droplets as described above, in aprocess of start up of a plant or when the ambient temperature isextremely low, only supply air is supplied. Consequently, in the formercase, operation wherein the discharged amount of NOx is controlled canbe performed, but in the latter case, the inlet air temperature can beraised, and operation wherein icing can be prevented can be performed.

In particular, in the construction which includes the control valve 14 bdescribed above, the control valve 15 is closed while only the controlvalve 14 b is opened so that only a desired amount of liquid dropletscan be injected into inlet air.

As liquid droplets are supplied from the atomizing nozzles 11, they canbe injected homogeneously into the inlet air, and the temperaturedistribution of the inlet air can be made homogeneous.

The embodiment further may include water recovery equipment 31 installedat an exhaust section of the turbine 2 and, in order to recover water inturbine exhaust gas and re-utilize the water as injection water, itfurther includes a path for supplying water recovered by the waterrecovery equipment 31 to the feed water tank 17.

For the recovery equipment, equipments which make use of variousprincipals such as steam condensation by cooling or physical absorptioncan be adapted.

Inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, and water recovered by the water recovery equipment 31is stored once into the water supply tank and then passes through thecontrol valve 15 of a predetermined opening and then through the feedwater means 13 so that fine droplets are thereafter injected from theatomizing nozzles 11. Where air supply from the air supply means 12 isnecessary to inject the fine droplets, the control valve 14 issimultaneously set to a predetermined opening to adjust the particlediameter of injected liquid droplets. The inlet air 6 contains theliquid droplets to form a mist flow, and the mist flow enters thecompressor 1 after part of it is evaporated to cool the inlet air. Theliquid droplets contained in the inlet air are evaporated in the insideof the compressor 1 to cool the compressed air.

After the liquid droplets are substantially evaporated in the compressor1, fuel is mixed with the compressed air and combusted in the combustor5 to produce gas of a high temperature and a high pressure, which thenflows into the works in the turbine 2. The mechanical energy isconverted into electrical energy by the generator 3, and the electricalenergy is supplied to the electric power grid 4. The exhaust gas aftercompletion of the work is discharged into the atmospheric air throughthe stack 8.

Accordingly, in addition to the effects of augmentation of the poweroutput of the gas turbine and augmentation of he thermal efficiency ofthe gas turbine, water can be utilized effectively, and saving of watercan be achieved.

It is to be noted that, in a gas turbine plant which includes a heatrecovery boiler 30, the water recovery efficiency can be augmented bydisposing the water recovery equipment 31 described above at the exit ofthe heat recovery boiler 30.

The fuel for the combustor 5 may be liquefied natural gas (LNG).Consequently, the embodiment may include a liquefied natural gas storagesection 33 which serves also as a cold heat source, and includes, as thewater recovery equipment 31, a heat exchanger 32 for raising thetemperature of natural gas supplied from the liquefied natural gasstorage section 33 to evaporate the natural gas and a path 34 forintroducing the evaporated natural gas to the combustor 5. The heatexchanger 32 is installed so as to utilize exhaust gas of the gasturbine.

Further, the heat exchanger 32 recovers water in the exhaust gas. Inorder to recover water in the exhaust gas and re-utilize the water asinjection water, the heat exchanger 32 includes a path 32A for supplyingthe water recovered by the heat exchanger 32 to the feed water tank 17.

Here, in addition to the effects of augmentation of the power output ofthe gas turbine and augmentation of the thermal efficiency of the gasturbine, such effects that an equipment for evaporation of LNG isunnecessary and that water can be recovered are obtained. Also effectiveutilization of non-utilized energy is achieved.

The present embodiment also may include a combination of water injectioninto inlet air and inlet air cooling equipment.

Specifically, a cooling coil 35 connected to an external cold heatsource 36 is provided on the rear face of the louver 9 and a cold heatmedium is circulated by a pump 42. The cooling coil 35 may otherwise bedisposed on the front face of the louver 9.

Inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, whereafter it is cooled when it passes the cooling coil35, and water of the feed water tank 17 passes through the control valve15 of a predetermined opening and further through the feed water means13 so that fine liquid droplets are thereafter injected from theatomizing nozzles 11. Where air supply from the air supply means 12 isnecessary to inject the fine droplets, the control valve 14 issimultaneously set to a predetermined opening to adjust the particlediameter of injected liquid droplets. The inlet air 6 contains theliquid droplets to form a mist flow, and the mist flow flows into thecompressor 1 after part of it is evaporated to cool the inlet air. Theliquid droplets contained in the inlet air are evaporated in the insideof the compressor 1 to cool the compressed air.

After the liquid droplets are substantially evaporated in the compressor1, fuel is mixed with the compressed air and combusted in the combustor5 to make gas of a high temperature and a high pressure, which flowsinto and works in the turbine 2. The mechanical energy is converted intoelectrical energy by the generator 3, and the electrical energy is fedto the electric power grid 4. The exhaust gas 7 after completion of thework is discharged into the atmospheric air through the stack 8.

In the present equipment, in addition to the effects of augmentation ofthe power output of the gas turbine and augmentation of the thermalefficiency of the gas turbine which are achieved by the embodiment,increase of the power output is achieved by a synergetic effect ofincrease of the inlet air mass flow rate by cooling of the inlet air anddecrease of the work of the compressor 1 by injection of water.Typically, by setting the capacity of the cooling coil 35 so that it cancool to a dew point at which inlet air cooling can operate efficiently,a high increased power output can be obtained while saving water. Thepresent embodiment is advantageous where it is applied to a district inwhich shortage of water is forecast in summer.

A second embodiment of the present invention will be described withreference to FIG. 2. This embodiment clearly indicates, comparing withthe first embodiment, that the atomizing nozzles 11 are positioned inthe inlet air compartment adjacent the louver 9. FIG. 2 shows theatomizing nozzles 11 so as to facilitate understanding of the positionof them. While FIG. 2 shows a construction which includes air supplymeans 12 for supplying pressurized inlet air, such air supply means 12as in the embodiment 1 need not be provided only if such desired liquiddroplets as described above are obtained.

From the point of view to promote evaporation prior to flowing in to thecompressor 1 to raise the efficiency in cooling of inlet air, preferablythe atomizing nozzles 11 are disposed in a spaced relationship from theentrance of the compressor 1 in this manner.

Describing in more detail, the atomizing nozzles 11 are suitablydisposed at one of the positions 11 a or 11 b.

Where the inlet air compartment 10 includes a silencer 41, the atomizingnozzles 11 a are disposed on the downstream side of the silencer 41.

Consequently, also a sound insulating material can be prevented frombeing wet by the silencer. The atomizing nozzles 11 are preferablyinstalled at a distance to the compressor taking a flying distance overwhich liquid droplets are evaporated before they are introduced into thecompressor into consideration. Alternatively, the atomizing nozzles 11 bmay be disposed on the upstream side of the silencer.

For example, where the atomizing nozzles 11 b are disposed in theproximity and on the downstream side of the louver 9 in the inlet aircompartment, the distribution of water droplets in the inlet air can bemade more homogeneous before the water droplets enter the compressor.Further, where a portion of the louver 9 extends wider than the inletair compartment 10 on the downstream of the louver 9 or a like case,installation or maintenance of the atomizing nozzles 11 is easy.

Where the inlet air compartment 10 does not include a silencer, theatomizing nozzles 11 are positioned between the louver 9 and theentrance of the compressor 1. The atomizing nozzles 11 are preferablyinstalled at a distance to the compressor taking into consideration aflying distance over which liquid droplets are evaporated before theyare introduced into the compressor.

Inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, and then, where a silencer is present, the inlet air 6passes through the silencer. Meanwhile, water from the feed water tank17 passes through the control valve 15 of a predetermined opening andfurther through the feed water means 13 so that fine liquid droplets areinjected from the atomizing nozzles 11. Where air supply from the airsupply means 12 is necessary to inject fine liquid droplets, the controlvalve 15 is simultaneously set to a predetermined opening to adjust theparticle diameter of injected liquid droplets. The inlet air 6 containsthe liquid droplets to form a mist flow and flows into the compressor 1after it cools the inlet air. The liquid droplets contained in the inletare evaporated in the inside of the compressor 1 and cool the compressedair.

Consequently, recuperation of the power output of the gas turbine can beperformed further efficiently by a synergetic effect of the twoprinciples of increase of the inlet air mass flow rate and reduction ofthe compressor work by cooling of inlet air.

More particularly, if the injection nozzles are arranged at a locationspaced by suitable distance from the entrance of the compressor in theinlet air compartment, then since part of the injected water isevaporated to cool the inlet air to a temperature in the proximity ofthe wet bulb temperature, similar effects are exhibited although somedifference may be present from those obtained where an air cooler isinstalled in an inlet air flow path. The working fluid of the compressor1 can be cooled effectively both inside the compressor 1 and outside thecompressor 1, and the power output increase can be made larger where thedistance is provided than where the atomizing nozzles 11 are arranged inthe proximity of the entrance of the compressor.

FIGS. 5 and 6 illustrate a status variation of the working fluid and arelationship between the inlet air temperature and the inlet mass flowrate in the process wherein external air is introduced into andcompressed by the compressor 1, respectively.

FIG. 5 illustrates a status variation where the ambient conditions areset to 30° C. and 70% in relative humidity (R.H.).

The ambient condition is indicated by a point A. If it is assumed thatexternal air is evaporatively cooled along a constant wet bulbtemperature line on a psychrometric chart until it enters a saturationstate before it flows into the compressor, then the state of the inletair changes to a state B at the entrance of the compressor 1. Thehumidity of gas to be introduced into the compressor 1 by injection ofliquid droplets described above is preferably raised approximately to90% or more from the point of view to maximize evaporation prior tointroduction into the compressor. From the point of view to achievebetter cooling of inlet air, the humidity should be raised to 95% ormore. Those liquid droplets which have not been evaporated in the inletair compartment 10 are continuously evaporated in the compressionprocess from B to C. If it is assumed that saturation is kept during theprocess of evaporation, then boiling is completed with the state C, andin the process from C to D, single phase compression is entered and thetemperature rises. If it is assumed that evaporation is an isoentropicprocess, the boiling end point comes to super-saturation of the stateC′. Since the evaporation rate from liquid droplets is actually finite,it is considered that the state variation is non-isothermal and followsa locus of a broken line displaced from a saturation line. In contrast,in an ordinary compression process, the status traces the locus from Ato D′.

Where, in FIG. 5, the temperature at A is represented by T1 and thetemperature at B is represented by T1′, the inlet air flow rate increasewhen the temperature drops from T1 to T1′ increases from W to W′ asschematically shown in FIG. 6. The remaining liquid droplets areintroduced into and evaporated in the compressor 1 so that theycontribute to reduction of the work of the compressor 1.

FIGS. 9(a) and 9(b) illustrate a relationship between the water dropinjection amount and the increasing rate of the power output of the gasturbine. FIG. 9(a) illustrates a variation of the power output relativevalue to the inlet air temperature, and FIG. 9(b) illustrates arelationship between the injection amount and the power output increase.

Values illustrated are obtained where the calculation conditions are,for example, 35° C. in ambient condition, 53% in relative humidity, 417kg/s in compressor air capacity characteristic, 0.915 in compressorpolytropic efficiency, 0.89 in turbine adiabatic efficiency 1,290° C. incombustion temperature, 20% in compressor extraction quantity, 1.48 MPain discharge pressure, and 0.25 MPa in evaporation stage pressure drop.If water at room temperature is injected, then 0.35% of the inlet airflow rate is evaporated in the inlet air compartment before it flowsinto the compressor. Consequently, as the inlet air temperature dropsand the density of air rises, the inlet mass flow rate of the compressorincreases by several %, which contributes to power output increase ofthe gas turbine. The remaining injected water accompanies the air flowand is sucked, while remaining in the form of liquid droplets, into thecompressor, in which it is evaporated and contributes to reduction ofthe work of the compressor.

The thermal efficiency augmentation ratio upon 2.3% injection is 2.8% inrelative value. The consumed water amount necessary to recuperate thepower output of the gas turbine to an output exhibited upon 5° C. baseload operation is approximately 2.3 weight % of the inlet mass flowrate. Details of output increase when operation is performed until theoutput of the gas turbine is recuperated to a maximum value, are roughlyestimated as follows: the portion which is based on cooling before thecompressor 1 is entered is approximately 35%; the portion which is basedon cooling by evaporation in the inside of the compressor isapproximately 37%; and the portion which is based on a difference inamount of the working fluid which passes through the turbine and thecompressor and increase of the low pressure specific heat arising fromsteam contained in the working fluid is approximately 28%.

Though not shown on the scale of FIGS. 9(a) and 9(b), the injectionwater amount may be further increased so that power output increase upto an allowable power output level can be obtained with an injectionflow rate of approximately 5 weight %. As the injection amountincreases, the evaporation action of water droplets in the compressor 1has an increasing influence upon the power output increase by an action(cooling action) outside the compressor 1.

FIG. 12 illustrates a relationship of a difference between the dischargetemperatures of the compressor before and after injection to theinjection amount. It can be seen that evaporation and cooling beforeliquid droplets flow into the entrance of the compressor 1 can beperformed efficiently with a low flow rate. The humidity which isreached by the inlet air flowing into the entrance of the compressor 1is in the proximity of approximately 95%. The solid line indicates adifference between the temperature of gas at the exit of the compressor1 and the temperature prior to injection calculated from two conditionsthat the absolute humidity of the gas at the exit of the compressor 1and the enthalpy of gas at the exit of the compressor 1 calculated underthe assumption that liquid droplets flowing into the compressor 1 areevaporated by the entire amount are equal to those values prior to theinjection. The line is obtained under the assumption that there is noreduction in power. However, actual values indicated by blank roundmarks (interconnected by a broken line for facilitated understanding)are higher than those values presented by the line, and reduction inpower is actually present. This arises from the fact that thetemperature drop amount by evaporation is amplified in a compressionstep in a stage later than the evaporation point.

Also from this, it is considered that the evaporation amount of liquiddroplets introduced into the compressor 1 by the atomizing nozzles 11 onthe front stage side is preferably made larger than the evaporationamount on the rear stage side and to evaporate liquid dropletsintroduced into the compressor 1 principally on the front stage side iseffective to reduction in power.

Liquid droplets are injected by such an amount that the temperature ofcompressed air discharged from the compressor 1 is lowered by 5° C. ormore from that prior to the injection. From the point of view to achievefurther increase in power output, the amount of liquid droplets is setto such a degree that the temperature is lowered by 25° C. or more. Itis to be noted that the upper limit can be determined from the point ofview of practical use. For example, it is reasonable to set the amountof liquid droplets so that the temperature is lowered by 50° C. or less.

A further aspect of the embodiment of FIG. 1 will now be described.

The embodiment of FIG. 1 further includes a mechanism which can controlthe temperature of liquid droplets to be injected.

The embodiment of FIG. 1 may include a heat recovery boiler 30 whereinexhaust gas of the turbine 2 is used as a heat source. Further, throughnot shown in FIG. 1, a steam turbine which is driven by steam generatedby the heat recovery boiler 30 maybe provided. Further, at least agenerator which is driven by the gas turbine or the steam turbine may beprovided. The air supply means 12 includes a path 12A for supplyingsteam generated by the heat recovery boiler 30 to the atomizing nozzles11, and a control valve 14 c is disposed in the path.

Inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, and water of the feed water tank 17 passes through thecontrol valve 15 of a predetermined opening and then through the feedwater means 13 so that fine liquid droplets are injected from theatomizing nozzles 11. In this instance, the steam supply amount iscontrolled by the control valve 14 c.

Further, where compressed air is supplied to the atomizing nozzles 11additionally, the amount of compressed air can be controlled by thecontrol valve 14 a provided in the path from the accumulator 29 to theatomizing nozzles 11.

Consequently, since the heating temperature can be adjusted, thetemperature of liquid droplets to be injected and so forth arecontrolled. The inlet air 6 contains the liquid droplets of the desiredtemperature to form a mist flow, which flows into the compressor 1 afterit cools the inlet air. The liquid droplets contained in the inlet airare evaporated in the inside of the compressor 1 and cool the compressedair.

According to the present embodiment, in addition to achievement ofaugmentation of the power output of the gas turbine of the embodiment 1and augmentation of the thermal efficiency of the gas turbine, theevaporation rate of liquid droplets can be controlled by controlling thetemperature of injection liquid. If the water temperature is raised,then evaporation of liquid droplets can be shifted to the front stageside of the compressor. Consequently, the work amount of the compressor1 can be further reduced. While the temperature of water droplets to beinjected varies depending upon conditions, the appropriate range forpractical use is 10 to 80° C. As a method of controlling the watertemperature, in addition to a method of mixing steam into the injectionnozzles, control 6f the bleed extraction gas temperature of thecompressor or a system which controls using temperature controllingmeans such as a heater 51 provided at a suitable location of the feedwater means 13 may be employed.

Where the air supply means 12 described hereinabove is not provided, itis effective to provided the heater 51. In the method shown in FIG. 1wherein steam is supplied, provision of the heater 51 is effective in acombined plant, particularly a cogeneration plant, since steam can beutilized effectively. The heater 51 is effective since steam of the heatrecovery boiler 30 can be utilized even where separately providedheating means or the like is not disposed. It is to be noted thatseparate steam generation means may be provided.

It also is effective to mix combustible liquid having a high steampartial pressure into injection water. For example, mixture of water andalcohol or the like is injected from the atomizing nozzles 11. Forexample, antifreezing solution is used. Where glycerin or ethyleneglycol is added to water to form mist, the reduction efficiency of thepower of the compressor is high since it volatilizes at a lowtemperature. Further, since the freezing point drops, there is nopossibility of icing of liquid droplets even in winter or the like.

For a concrete construction in a season such as winter, glycerin orethylene glycol is added into the feed water tank 17 and stored asmixture in the feed water tank 17.

The gas turbine of the present embodiment can augment the thermalefficiency also upon part load operation.

Steam may be supplied into inlet air to be introduced into thecompressor 1 in the embodiment of FIG. 1.

More particularly, the gas turbine includes a path 12A for supplyingsteam generated by the heat recovery boiler 30 to the air supply means12 so that steam supplied from the atomizing nozzles 11 can be injected.

Inlet air 6 passes through the louver 9 and comes into the inlet aircompartment 10, and the control valve 15 is closed. Steam generated bythe heat recovery boiler 30 passes through the control valve 14 c of apredetermined opening and then through the air supply means 12 so thatit is injected from the atomizing nozzles 11. If it is assumed that theair supply means 12 is not provided but only the feed water means 13 isprovided, though not shown, the gas turbine may be constructed suchthat, in place of supply water from the feed water tank 17, the steam issupplied from the feed water means 13 to the atomizing nozzles 11. Or,though not shown, in addition to the atomizing nozzles 11, separatelyprovided steam supplying nozzles to which steam generated by the heatrecovery boiler 30 is supplied may be disposed. It is to be noted thatthe amount, the temperature or the like of steam to be injected intoinlet air is controlled, although it is different depending upon thesteam source, by an aimed temperature of inlet air to enter thecompressor 1.

The inlet air 6 whose temperature has been controlled to the desiredtemperature is flowed into the compressor 1.

According to the feature just described of the embodiment of FIG. 1, fora thermal efficiency augmentation method for part load operation, thefollowing method can be used.

For example, in winter or a like season, when such a situation that thedemand for power is less and part load operation cannot be avoided isentered, by injecting steam into inlet air as described above, the inletair temperature which has been, for example, approximately 10° C. can beraised to approximately 50° C. before it is supplied to the compressor1.

Since the temperature of inlet air can be raised by injecting steam intothe entrance of the compressor, the density of the air decreases and theinlet mass flow rate of the compressor decreases, and consequently, thepower output of the gas turbine can be reduced while suppressing drop ofthe thermal efficiency. This is because base load operation can beperformed while avoiding part load operation of the gas turbine.

This feature is effective when the demand is reduced depending upon aseason since, even when the requested load decreases and the poweroutput is to be reduced, since the operation having the thermalefficiency higher than that achieved by a conventional part loadoperation method by IGV control or the like can be performed.Particularly in a plant wherein steam is generated using exhaust gas ofa gas turbine such as a combined cycle plant or a cogeneration plant,also effective utilization of surplus steam can be achieved sinceresidual steam can be used for generation.

It is to be noted that, as the case may be, instead of using steam for aheat recovery boiler, separate steam generation means may be provided.

The embodiment of FIG. 1 further may include means such as a nozzle forsending pressurized air to a mid stage of a compressor.

A flow control valve 47 may be provided in a line 59 for feedingcompressed air supplied from a compressed air source 43 to a mid stageof the compressor 1. The compressed air source 43 can supply air from acompressor installed outside or an atomization compressor for fuelinjection. Alternatively, although the effect is somewhat inferior airmay be recirculated from a discharging location of the compressor 1. Inthis instance, since a lower temperature of the bleed provides a higherthermal efficiency, cooling means 48 is preferably providedintermediately of the feed air line 59.

If liquid droplets 37 are evaporated to cool air in the compressor 1,the density of the air becomes higher, and consequently, an axialvelocity 46 drops. Consequently, the velocity triangle is distorted asseen in FIG. 10, and the incident angle of an air flow to a blade 45 isdisplaced from a designed value like from 46 a to 46 b, and a reverseflow develops along the face of the blade. Consequently, the adiabaticefficiency of the compressor 1 drops. As the adiabatic efficiency drops,the discharging temperature of the compressor 1 rises, and as a result,the reduction effect of the work of the compressor decreases. Since itis considered that this phenomenon becomes more significant as theinjection water amount increases, limitation is applied to the injectionamount in a practical phase. In order to eliminate this, the axialvelocity should be recuperated by feeding air to the compressor 1. Asthe position at which air is fed, a position at which evaporation ofwater droplets is substantially completed is selected effectively.Preferably the feed air amount is selected as a function of theinjection amount so that the axial velocity may be held at is designedvalue even if the injection amount varies.

The opening of the control valve 15 for a water amount is increased andthe opening of the flow control valve 47 is increased by an instructionsignal from the function generator 24 in response to an increase of anaimed power output based on the power demand signal 25.

The amount of water to be supplied from the control valve 15 and theamount of compressed air to be supplied from the flow control valve 47may have a relationship of a monotone increasing function.

Upon decrease of the power output, the openings of the valves mentionedabove are controlled so as to be decreased.

By this construction, the restriction to the injection amount ismoderated, and the width of power decrease of the compressor per unitair flow rate increases since no degradation of the adiabatic effect isinvited. Further, also the effect that the power output increase of thegas turbine is increased by increase of operating liquid by air feedingis exhibited.

A third embodiment of the present invention will be described withreference to FIG. 3.

The third embodiment is constructed such that, in a gas turbine of thetype wherein bleed extraction of the compressor 1 is supplied into acooling flow path formed in a turbine blade to cool the turbine blade,the bleed extraction flow rate is controlled in response to thetemperature of the bleed extraction of the compressor.

Instead of feeding compressed air to a mid stage of the compressor 1 ofthe type wherein a turbine blade is cooled, the flow rate after thebleed extraction stage can substantially be increased by decreasing thebleed extraction quantity from a bleed extraction line 56 of thecompressor 1, which is provided for cooling the turbine blade, inconformity with a drop of the temperature of the bleed extraction gas.

To this end, a flow control valve 55 or a motor valve with anintermediate opening set is provided in the bleed extraction line 56.

If water droplets are evaporated to cool air in the compressor 1, thensince also the temperature of the bleed extraction drops, the amount ofair required for bleed extraction of the compressor for cooling theblades of the turbine may be small. The bleed extraction may have arelationship of a monotone decreasing function with the flow controlvalve 55 using an instruction signal from a bleed extraction amountcontrol function generator 58 in response to a decrease of an aimedbleed extraction quantity based on a temperature signal of a temperaturedetector 57 which detects the temperature of the bleed extraction.

Where a motor valve with an intermediate opening set is used, theopening of the valve is controlled to a predetermined value in responseto a temperature when the bleed extraction temperature reaches a presetvalue.

Since the amount of air of the compressor at a stage following the bleedextraction point can be increased by decreasing the bleed extractionamount, the axial velocity is recuperated and the adiabatic efficiencyof the compressor is augmented, and the temperature of gas at the exitof the compressor drops and the power of the compressor per unit airamount decreases. Further, since the amount of air supplied to theturbine increases, the shaft power increases. Those actions furtheraugment both of the power output and the heat efficiency.

As regards the embodiments which relate to a gas turbine describedabove, they can be applied to a combined cycle plant which employs thegas turbine and includes a heat recovery boiler which generates steamusing exhaust gas from the turbine as a heat source and a steam turbinewhich is driven by the steam generated by the heat recovery boiler.

Consequently, augmentation of the power output and augmentation of theheat efficiency of the combined cycle plant can be achieved by such asimple apparatus which is suitable for practical use as described above.

Further, even if each of the embodiments is regarded as a single unit ofa compressor, reduction of required power of the compressor can berealized by a simple apparatus.

In particular, if such fine liquid droplets as described above areinjected into inlet air supplied to the entrance of a compressor so thatthey are evaporated in the compressor, then the following principaleffects described above can be achieved. In this instance, for the gasto be supplied into the compressor as the inlet air, ammonia, freon andso forth can be used in addition to air. Further, for liquid droplets tobe injected, where air is used, water and so forth can be used asindicated in the examples of gas turbine described hereinabove. In thecase of a compressor wherein ammonia is employed as the inlet air,liquid ammonia can be injected, but where freon gas is employed as theinlet air, liquid freon can be injected.

Comparing with an alternative case wherein liquid droplets and mist arenot mixed into inlet air to enter the compressor, part of them isevaporated to cool the inlet air before it enters the entrance of thecompressor 1 while water droplets can be evaporated continuously fromthe entrance portion of the compressor, and consequently, the gastemperature in the compressor exhibits a continuous drop. Also thedischarge temperature drops. Furthermore, when the liquid dropletsintroduced into the compressor are evaporated in the compressor toincrease the mass flow rate and then evaporation is substantiallycompleted in the compressor, then the gas in the compressor is subjectto adiabatic compression, and there is an effect similar to that of anincrease of the working fluid. If the injection amount is increased,then also the compressor power ratio (isoentropic compression work ofdry air/compression work in an isoentropic two phase compression processincluding evaporation of liquid) can be further reduced.

Further, even if each of the embodiments described above is regarded asa liquid droplet injection apparatus for injecting liquid droplets intoinlet air of the compressor of the gas turbine, augmentation of thepower output and augmentation of the thermal stress of the gas turbinewhich includes the apparatus can be realized with a simple apparatus.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit and scope of theinvention as set forth herein.

What is claimed is:
 1. A liquid droplet injection device for a gasturbine comprising a compressor, a combustor and a turbine, said liquiddroplet injection device comprising: a filter or a louver disposed on anupstream side of the compressor; atomizing nozzles disposed between thecompressor and said filter or said louver which is disposed on theupstream side of the compressor; feed water means connected to saidatomizing nozzles; and a control device having means for controlling anamount of liquid droplets to be injected into the inlet air to besupplied to the compressor, said control device controlling the amountof liquid droplets such that the liquid droplets are partiallyevaporated in the inlet air to cool the inlet air to be supplied intothe compressor, and the remaining injected liquid droplets are suppliedinto the compressor together with the inlet air and are furtherevaporated in the compressor.
 2. A liquid droplet injection deviceaccording to claim 1, wherein said control device includes means forcontrolling the amount of liquid droplets to be injected in response toan ambient temperature.
 3. A liquid droplet injection device accordingto claim 1, wherein said control device includes means for controllingthe amount of liquid droplets to be injected in response to an output ofthe gas turbine.
 4. A liquid droplet injection device according to claim2, wherein said control device includes means for controlling the amountof liquid droplets to be an amount equal to 0.2 to 5.0 weight % of themass flow rate of the air.
 5. A liquid droplet injection deviceaccording to claim 3, wherein said control device includes means forcontrolling the amount of liquid droplets to be an amount equal to 0.2to 5.0 weight % of the mass flow rate of the air.
 6. A liquid dropletinjection device according to claim 1, wherein said liquid dropletinjection device includes means for injecting liquid droplets havingdroplet diameters principally from 1 to 50 μm.
 7. A liquid dropletinjection device according to claim 2, wherein said liquid dropletinjection device includes means for injecting liquid droplets havingdroplet diameters principally form 1 to 50 μm.
 8. A liquid dropletinjection device according to claim 3, wherein said liquid dropletinjection device includes means for injecting liquid droplets havingdroplet diameters principally from 1 to 50 μm.
 9. A liquid dropletinjection device for a gas turbine comprising a compressor, a filter ora louver disposed on an upstream side of the compressor, a combustor anda turbine, said a liquid droplet injection device comprising: atomizingnozzles disposed between the compressor and the filter or the louverwhich is disposed on the upstream side of the compressor; feed watermeans connected to said atomizing nozzles; and a control device havingmeans for controlling an amount of liquid droplets to be injected intothe inlet air to be supplied to the compressor, said control devicecontrolling the amount of liquid droplets such that the liquid dropletsare partially evaporated in the inlet air to cool the inlet air to besupplied into the compressor, and the remaining injected liquid dropletsare supplied into the compressor together with the inlet air and arefurther evaporated in the compressor.